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Study suggests link between birth defects, drilling

Researchers analyzing Colorado data say the risk of two birth defects appears to increase with closer proximity of mothers to natural gas wells.

The study draws on data from the Colorado Department of Public Health and Environment, but that department immediately distanced itself from the findings, calling them inconclusive and potentially misleading. The study also found a decrease in some birth-related health problems for mothers living near wells.

The study was conducted mostly by researchers with the Colorado School of Public Health. It found that babies born to mothers living within a mile of at least 125 natural gas wells experienced a 30 percent greater prevalence of congenital heart defects, compared to those born to mothers living no closer than 10 miles from wells. It also found an association between mothers living within a mile of 125 or more wells and an increased occurrence of newborns’ neural tube defects, which affect the brain, spine or spinal cord.

However, it found no link between rates of cleft lips and palates in newborns and a mother’s proximity to wells.

It also found what it called an “unexpected” result of a 10 percent decreased risk of preterm birth with mothers’ increasing exposure to natural gas development, and also a decreased risk of low birth weight for full-term babies born to such mothers.

The study analyzed nearly 125,000 live births from 1996 to 2009 and excluded cities with populations over 50,000 to reduce the potential for exposure to traffic, industry and other pollution sources. It suggested that exposures to benzene and air pollutants from truck traffic could account for some of the birth-defect associations it found.

The study says exposure to natural gas development is increasingly common, with the Colorado Oil and Gas Conservation Commission estimating that 26 percent of the more than 47,000 oil and gas wells in the state are located within 150 to 1,000 feet of homes and other buildings intended for human occupancy.

“Taken together, our results and current trends in (natural gas development) underscore the importance of conducting more comprehensive and rigorous research on the potential health effects” of that development, the study says.

Dr. Larry Wolk, executive director and chief medical officer for CDPHE, acknowledged in a media statement the public concern about the effects of oil and gas operations on public health, including birth outcomes.

“While this paper was an attempt to address those concerns, we disagree with many of the specific associations with the occurrence of birth defects noted within the study. Therefore, a reader of the study could easily be misled to become overly concerned.

“As Chief Medical Officer, I would tell pregnant women and mothers who live, or who at-the-time-of-their-pregnancy lived, in proximity to a gas well not to rely on this study as an explanation of why one of their children might have had a birth defect. Many factors known to contribute to birth defects were ignored in this study.”

Wolk cited study limitations including lack of knowledge of where mothers lived during the first trimester of pregnancy, when most birth defects occur. Noting the incongruity of decreased risk of certain problems that it found near wells, he called those findings “counterintuitive” and another thing that makes the study difficult to interpret.

He also noted that the study only found an association between certain defects and drilling, rather than a causal link, and said that the “statistical differences in birth defects were miniscule.”